Howard County officials are unveiling bills to limit infill development in older neighborhoods by transferring density to other areas and curtailing certain building practices, initiatives expected to spark wide-ranging debate.

County Council Chairman Courtney Watson (D-Northeast County), a principal sponsor of the legislation, said infill development was a chief concern for voters in her district when she ran for the council in 2006. She has spent months working with the administration of County Executive Ken Ulman (D) on initiatives to preserve open lots, impose stricter environmental controls and limit new lots that share a single driveway.

"It's compatibility and protecting the integrity of existing neighborhoods," Watson said, adding that the measures focus on older, single-family neighborhoods in areas such as Elkridge, with large lots that can be subdivided.

However, Tom Ballentine, with the Home Builders Association of Maryland, said Tuesday: "We have to oppose parts of this package. The proposal goes far beyond the neighborhood issue of infill."

The measures are scheduled to be discussed by the Planning Board at 7 tonight at the George Howard Building, 3430 Courthouse Dr., in Ellicott City. The public is invited to comment.

Community activists called limiting infill development in eastern Howard a top priority.

"It affects individuals intensely and directly. It's happening next door," said Bridget Mugane, president of the Howard County Citizens Association. "This causes friction."

One measure allows owners of large lots in neighborhoods to sell building rights on undeveloped property, permanently preserving the lot. The building rights, usually amounting to a few housing units, could be purchased by developers for use in specified, higher-density areas, such as neighborhoods of townhouses, apartments and condominiums. That "bonus density" would allow the developer to exceed the usual maximum number of units per acre.

"The buying and selling of building rights is done at a very small scale, onesies and twosies," said Watson. "It's not so much that it's going to cause many problems in the surrounding area."

Even so, community activist Angela Beltram noted that one of the neighborhoods that could receive additional density is Turf Valley Resort and Conference Center, the county's sole planned golf course community. Turf Valley, on 809 acres west of Ellicott City, has encountered resident opposition to long-standing plans for a major expansion that includes more than 1,600 housing units, retail space and offices.

"The transfer elsewhere is what I'm concerned about," Beltram said of units. She added that the County Council, which will consider the legislation after the Planning Board, should know exactly how many areas could receive additional density.

Another bill imposes new environmental controls and limits the development of pipestem lots, residential lots that share a driveway.

"When you are developing in a neighborhood that's already established, it requires greater sensitivity than what's there now in the regulations," said Kimberley Flowers, deputy director for public affairs in the Department of Planning and Zoning. For example, she said, protecting mature trees and requiring more storm-water management study can maintain residents' privacy and keep runoff out of their basements.

But Ballentine, director of policy for government affairs with the home builders, said the new regulations on pipestem lots and storm-water management can apply anywhere in Howard, not just in established neighborhoods.

"The focus should specifically be on redevelopment of existing building lots and not stray into the western part of the county," he said.

Trying to comply with tighter storm-water management regulations "could be an expensive undertaking for the average homeowner" who's looking to remodel, build a deck or do new landscaping, he said.

"The question is whether property owners are aware of this," Ballentine said.